Select fire jet perforating apparatus

ABSTRACT

JACENT ELECTRODE WHICH CAN BE SUBSEQUENTLY CONTACTED BY A SOURCE OF CURRENT SO AS TO DETONATE THE PERFORATING MEANS TO WHICH IT IS ELECTRICALLY CONNECTED.   A PERFORATING APPARATUS HAVING SEPARATE CHAMBERS FORMED THEREIN, AND WITHIN WHICH THERE IS DISPOSED ELECTRICALLY ACTUATED EXPLOSIVE PERFORATING MEANS. THE APPARATUS INCLUDES A FIRING HEAD HAVING A PLURALITY OF ELECTRODES RECEIVED THEREIN AND SUPERIMPOSED ONE UPON ANOTHER AND ELECTRICALLY INSULATED FROM ONE ANOTHER. ONE OF EACH ELECTRODE IS ELECTRICALLY CONNECTED TO AT LEAST ONE OF THE PERFORATING MEANS SO THAT WHEN A SOURCE OF CURRENT IS APPLIED TO THE ELECTRODE IT DETONATES THE PERFORATING MEANS, WHEREAFTER THE ELECTRODES IS REMOVED FROM THE FIRING HEAD SO AS TO OPERATIVELY EXPOSED THE NEXT BELOW AD-

1973 R. R. VANN 3,7115

SELECT FIRE JET PERFORATING APPARATUS Filed June '7, 1971 ii ya MARCUSLBATES H/5 HGEN? United States Patent 3,717,095 SELECT FIRE JETPERFORATING APPARATUS Roy R. Vann, Midland, Tex. (Box 40-A, Star Rte.W., Artesia, N. Mex. 88210) Filed June 7, 1971, Ser. No. 150,304 Int.Cl. E21b 43/116 US. Cl. 102-21.6 Claims ABSTRACT OF THE DISCLOSURE Aperforating apparatus having separate chambers formed therein, andwithin which there is disposed electrically actuated explosiveperforating means. The apparatus includes a firing head having aplurality of electrodes received therein and superimposed one uponanother and electrically insulated from one another. One of eachelectrode is electrically connected to at least one of the perforatingmeans so that when a source of current is applied to the electrode itdetonates the perforating means, whereafter the electrode is removedfrom the firing head so as to operatively expose the next below adjacentelectrode which can be subsequently contacted by a source of current soas to detonate the perforating means to which it is electricallyconnected.

BACKGROUND OF THE INVENTION Oil and gas well completion techniques oftenrequire closely spaced multiple perforating at selected depths so as toperforate downhole piping or casing at various selected elevations in awell. Usually a single perforation at a particular depth is required,however, the perforation must be formed at precisely the elevationwithin the borehole which the geologist has determined to be the mostoptimum location. It is customary to detonate one or a group of theshaped charges, after which the gun apparatus is repositioned adjacentto the next desired level whereupon the gun is again fired so as toprovide the next perforation. This sequence of events is generallycontinued until all of the desired perforations have been made.

Several prior art patents teach the fabrication of a select firingsystem for use downhole in a borehole for selectively firing a jetperforator as evidenced by the patents to Coleman, 3,010,396; Boop,3,208,378; and Bell, 3,246,707, to which reference is made for furtherbackground of this invention.

The prior art apparatus generally includes complicated circuitry andmechanism which generally depends upon energy derived from eachexplosion so as to sequentially arm the next above adjacent shapedcharge apparatus associated with the gun apparatus. Usually, a singlemisfire precludes further detonation of the remaining charges andpresents a dangerous situation in that the misfire must be broughtuphole and disarmed.

It is desirable to make available a select fire jet perforationapparatus which can be positioned downhole in a borehole and the gunfired in a manner whereby each of the charges are positively exploded asa result of direct control exercised from above the surface of theground.

It is furthermore desirable to provide a jet perforating apparatus whichcan be continued in the sequential firing thereof even though one of thecharges should fail to fire.

It is further desirable to have made available a select fire jetperforating apparatus which has a minimum of moving parts, is simple indesign, and which is fool-proof in operation.

SUMMARY OF THE INVENTION This invention comprehends a perforatingapparatus having separate chambers formed therein within which there isdisposed electrically actuated explosive perforating means. Theperforating means is detonated by a power package which is brought intoelectrical contact with a firing head. The head has disposed therein aplurality of electrodes each superimposed upon and spaced apart from andinsulated from one another. Each electrode is removably received withinthe firing head and has associated therewith means by which it can beremoved therefrom. Circuit means electrically connect each electrode toat least one of the explosive perforating means, and each of theelectrodes are adapted to be removed one at a time from the firing head.A self-contained supply of current can be run downhole on a slick lineto where it contacts the uppermost electrode thereby detonating alowermost of the unexploded explosive charges.

Each electrode has associated therewith two branch circuits havingdiodes of opposite polarity arranged therein, with each diode beingconnected to the detonator of an explosive charge to thereby enable thesupply of current, when of the proper polarity, to cause sequentialdetonation of two adjacent lowermost explosive charges.

A primary object of this invention is the provision of a system forselectively firing a plurality of well casing perforating guns.

Another object of the invention is to provide a selective firing systemfor a plurality of perforating guns.

A further object of this invention is the provision of circuitry andapparatus for selectively and sequentially detonating a plurality ofsub-surface explosive devices.

A still further object of the present invention is to provide apparatusfor perforating the wall of a borehole, and which is inexpensive tomanufacture, simple to operate, and dependable in performance.

Another and still further object of this invention is the provision of areliable system for selectively and separately detonating one of aplurality of shaped charges in a predetermined sequential manner.

An additional object of the present invention is the provision of apositively acting arming means which preferably is actuated after thepreceding shaped charges have been detonated in a predeterminedsequence.

These and various other objects and advantages of this invention willbecome readily apparent to those skilled in the art upon reading thefollowing detailed description and claims and by referring to theaccompanying drawings.

The above objects are attained in accordance with the present inventionby the provision of a combination of elements which are fabricated in amanner substantially as described in the above abstract and summary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematical representationwhich shows the present invention as being operatively disposed within aborehole;

FIG. 2 is a diagrammatical presentation of the present invention;

FIG. 3 is an enlarged part cross-sectional fragmentary side view of thepresent invention;

FIG. 4 is a cross-sectional view taken along line 44 of FIG. 3;

FIG. 5 is an enlarged part cross-sectional view of part of the apparatusdisclosed in FIG. 3;

FIG. 6 is an enlarged cross-sectional view taken along line 6-6 of FIG.5; and

FIG. 7 is a reduced schematical representation of part of the presentinvention, showing one detail of operation thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG.1, there is seen a borehole which has been formed through the surface ofthe earth 10, within which there is disposed oil well casing and tubingflow connected to a Christmas tree 11. Production tubing 12 has a packer13 attached thereto and supports a perforated nipple 14. Numeral 15generally indicates various oil bearing strata from which hydrocarbonproduction may be obtained.

A power package 19 is connected to a slick line 19'. A firing head 18forms the upper marginal end of a perforating apparatus. The appartusincludes a gun 20 connected by sub 21 to an Other gun 22, with each ofthe guns having at least one chamber formed therein and with eachchamber containing electrically actuated explosive perforating means.

Looking now to FIGS. 2, 3, and 4, in conjunction with the remainingfigures, the before mentioned power pack is in the form of aself-contained electrical supply and is seen to include contact means at26 which is electrically connected to a double pole double throw switch27 which in turn is connected to a storage battery by means of thecircuitry 28.

Electrode assembly 29, which can be the uppermost electrode, has anupstanding portion thereof which is axially aligned with thelongitudinal axis of the firing head. Circumferentially spaced from theelectrode and connected to the exterior metal portions which houses thefiring head is a series of radially spaced apart grounding springs 30which preferably are in the form of inwardly directed spring steelwires. Insulation 31 is formed into a series of communicatingcounterbores, each having the illustrated shoulders so as to receive andsupport each of the electrodes 29, 32, and 33 thereon. While threeelectrodes are disclosed, it should be understood that two or more canbe employed while remaining with in the teachings of this invention.

Electrical conduit 34 is connected to the uppermost electrode andcontinues down through the interior of the gun assembly to junction 34where the circuitry branches, as one leg continues to the resistor R,the diode 35, the electrically fired cap C and to ground so as tocomplete the circuit. The cap is attached to the prima cord P, whichdetonates an explosive charge. =From junction 34' the remaining leg ofthe branch continues to the illustrated resistor and to the diode 35.'From diode 35 the circuit leads to a cap associated with prima cord andan explosive charge.

Electrical conductor 36 is connected to the before mentioned secondelectrode 32 and to diodes 37', 37. Diode 37' is electrically connectedto the explosive charge at 38 while diode 37 is connected to theexplosive charge located within chamber 120.

The lowermost electrode 33 is anchored to a bulkhead and electricallyconnected to the two uppermost explosive containing chamber, with thecircuitry splitting into two brances at 39 to enable current to flow at42 or 142 so as to provide a source of current within chambers 20 and22. The remaining branch circuit provides a flow path from junction 39through resistor 142 to the electrically detonated cap 43, primer cord143 which is connected at 44 to the shaped charge 144, as in the beforedescribed manner. Closure member 45 prevents flow of fluid into thechamber 20.

Looking noW particularly to FIG. 4 in conjunction with FIG. 3, electrode32 is seen to have an outwardly directed base having a peripheral edgeportion 46 which reduces in diameter into the metallic currentconducting upstanding shaft-like portion 47.

A series of apertures 48 allow individual wire conductors to freely passtherethrough, such as conductor 34, 34 for example.

The insulator 31 has formed therethrough a first counterbore 49 whichreduces in diameter to form shoulder 5% and continues in a downwarddirection as counterbore 51 which reduces in diameter to form a secondshoulder 52, and with the last counterbore 53 terminating in a bulkheadat its lower extremity so as to seal the 4 interior of the uppermostchamber 20 from the counterbores.

Coupling 54 interconnects the firing head 18 with the uppermostexplosive containing chamber 20. Each of the coupling members, or subs21, provide a sealed passageway from one chamber 20 to another chamber22, for example. Furthermore, each of the subs include a cylindricalinsert member 57 having the illustrated 0- rings disposed thereabout soas to enable the insert to sealingly engage the interior passageway ofthe coupling member and at the same provide a scalable passageway 58.The last named passageway, after the wires are extended therethrough, isfilled with epoxy resin so as to provide a positive fluid seal forpreventing fluid flow thereacross. The contoured outwardly divergingpassageway at 59 cooperates with the plastic seal formed therewithin toprovide a high pressure seal assembly. Resilient washers 60, 61, 63 arestacked one upon another and when the threaded nut 62 compresses thewashers, the electrical conduits extending through passageways 68, 64are provided with a secondary seal. End portion 61 can also be providedwith resilient washers and a nut, such an expedient being an optionaldetail of design.

Where deemed desirable, the inserts 57 together with the wires and theepoxy filling may be made up as a preassembled unit with the length ofthe wire therebetween being of the proper value so that the tool may beassembled from prefabricated parts. Hence the inserts can be extendedinto the couplings where the wires are available for use in the variouschambers through which they extend.

Looking in particular again to 'FIG. 3, each of the electrodes 29, 32and 33 are seen to have attached thereto an electrical conduit such asillustrated at 34, 36. The insulated wire 34 is rigidly attached toelectrode 29 and continues through one of the apertures 48 of electrode32, for example, where the wire then continues at 34' and engagesterminal 134 by means of a bayonet or bananatype connection such as seenat 65. Alternatively, the connection at 65 can be a rigid connection andthe wire size selected so that when electrode 29 is picked up withsufficient force by an overshot, the wire will break some where betweenthe terminal and the electrode.

OPERATION In operation, the select firing jet perforating apparatus isplaced downhole in a borehole with the distance between the shapedcharges contained within a single gun 20 being selected in any desiredmanner and number so as to enable any particular perforation pattern tobe effected upon a zone 15'. Gun assembly 22 is spaced apart from gunassembly 20 a predetermined amount so as to place the second gunadjacent to another pay zone 15'. Other additional guns may be employed.

The firing head 18 is supported by the vent string, although thoseskilled in the art will realize and understand that the gun could beconnected directly to the production tubing, suspended within the casingby a wire line, or anchored to the casing wall by any number ofdiiferent expcdients.

When it is desired to fire the lowermost gun, a power package isadjusted to provide a polarity which corresponds with current flowthrough diode 35', and is run downhole on a slick line until electricalcontact is made so as to provide a difference in potential between theelectrode and the grounding wires. At this time current flows from theelectrode 29 along conductor 34 and to junction 34'. Since the currentpolarity is incorrect or opposite to that required for current flowthrough diode 35, the perforating charge associated therewith cannotpossibly be detonated. However, current can flow from junction 34',through resistor R, through diode 35', and to the detonator C which iselectrically detonated when the proper current values are imposedthereon. The cap C detonates prima cord P which in turn detonates one ofthe shaped charges,

as seen at 144. The shaped charge penetrates closure means 44, thecasing 9, and communicates the interior of the casing with a pay zone15'. Production fluid generally is allowed to enter the casing, flow upthe casing annulus, into the apertures of vent string 14, and on up theproduction tubing 12 to the Christmas tree 11 where the production flowcan be controlled.

The next lowermost unexploded gun 122 is fired by changing the polarityof the power package so that the current flow can now be traced from thepower package, through electrode 29, conductor 34, junction 34',resistor R, diode 35', and On to the remainder of the explosive train(not shown) of the gun 220.

The third gun 122 as well as the fourth gun 120 is to be fired byelectrode 32. Accordingly, an overshot 41, the details of which areknown to those skilled in the art, is run downhole on a slick line whereit engages the upstanding metallic portion of electrode 29. The overshotis lifted bringing with it the electrode and conductor 34 which detachesfrom the banana terminal located within the bulkhead of counterbore 53.After removal of the electrode 29, the power package is adjusted toproper polarity and again run downhole on a slick line where it againcontacts electrode 32. Assuming proper selection of polarity, thecurrent flow can be traced from the power package to the electrode 32,through conductor 36, to the junction where the circuitry splits intotwo branch legs, which one diode connecting the current flow to theexplosive charge 38 of gun chamber 122 and the remaining diode 37conducting current flow to the shaped charge of gun chamber 120, all asin the before described manner of the two lowermost guns.

The select firing of the apparatus is continued in this sequentialmanner until each of the pay zones have been properly perforated. Thenumber of individual guns 20, 22 will of course depend upon the numberof different formations 15 which are to be perforated.

Looking in greater detail again to FIG. 3, grounding electrodes 30, 30'are electrically connected to the firing head 18 so as to make aplurality of contacts relative to the outer peripheral wall surface ofpower package 19. Internally of the power package there is disposed theillustrated electrodes which are insulated from the wall of the packageand which engage the upstanding metallic portion of the electrode.Hence, current flows from the power package to the electrode, to thevarious circuitry associated with the blasting cap (or detonator), andback to ground by utilizing the entire gun housing and package housingas the return ground circuit.

FIG. 7 schematically illustrates an overshot 41 connected to a slickline 119, which has retrieved electrode 29 from the dot-dashed position29 so as to leave electrode 32 operatively disposed within the firinghead, ready to be contacted by power package 19.

It will occur to those skilled in the art to utilize mechanicallyactuated apparatus which can be reciprocated downhole so as to changethe polarity of the power package. One possible apparatus of this typeis disclosed in my cigpeirgdilng patent application Ser. No. 116,948,filed Feb.

Those skilled in the art will also envision the provision of acombination overshot and power package which will enable the two to becombined together into a single unit, and such an expedient isconsidered to fall within the comprehension of this invention.

Moreover, while only three electrodes have been disclosed for purposesof illustration, those skilled in the art will understand that anynumber of electrodes may be used, the limiting factor being the physicaldimensions of the firing head itself. Furthermore, it is consideredobvious to employ a current carrying wire line in lieu of the slick lineand power package, and such a variation is deemed to be within thecomprehension of this invention.

I claim:

1. A perforating apparatus having separate chambers 6 formed thereinwith each chamber containing electrically actuated explosive perforatingmeans;

a firing head, a plurality of electrodes contained Wlthm said firinghead, means by which said electrodes are electrically insulated from oneanother and super1mposed one upon the other and removably receivedwithin said firing head; means by which the uppermost of said electrodescan be contacted by a supply of electrical current;

means by which at least one said electrode can be removed from saidfiring head;

circuit means electrically connecting each electrode to at least one ofsaid electrically actuated explosive perforating means;

whereby: a supply of current can be electrically connected to theuppermost electrode to thereby detonate one of the explosive perforatingmeans, and upon removal of an uppermost electrode, an adjacent electrodecan be contacted by a supply of current so as to detonate the explosivecharge to which it is connected.

2. The apparatus of claim 1, and further including two diodes ofopposite polarity, said circuit means connecting one of said diodes toone said electrode and to one said explosive perforating means and asecond of said diodesto the last said electrode and to an adjacent ofsaid exploslve perforating means, whereby:

a lowermost explosive perforating means may be detonated and thereafterthe polarity of the current changed so as to detonate the remainingexplosive perforating means.

3. The apparatus of claim 1, wherein said firing head includesconcentrically arranged chambers of diminishing diameters with thelargest chamber being the uppermost chamber and communicating with theremaining chambers by means of shoulders,

said electrode having a base adapted to contact and be supported by ashoulder with said base being smaller in diameter than the chamberwithin which the electrode is disposed so as to enable removal thereof.

4. The apparatus of claim 3 wherein said electrode includes anupstanding portion which is adapted to be r trieved by an overshotapparatus.

5. The apparatus of claim 1 wherein said circuit means further includeselectrical detonation means connected from an uppermost electrode to twolowermost explosive charges; and, electrical detonating means connectedt another of said electrodes and to an uppermost two of said explosivecharges;

said circuit means further including means for preventing positivecurrent flow connected to one of said two lowermost explosive chargesand to one of Said uppermost explosive charges; and, means forpreventing negative current fiow connected to the remaining twolowermost explosive charges and to the remaining two uppermost explosivecharges.

6. The apparatus of claim 1 wherein an uppermost electrode is connectedto a lowermost explosive perforating means, and a lowermost electrode isconnected to an uppermost explosive perforating means.

7. The apparatus of claim 1 wherein said circuit means includes anelectrical conductor connected from said electrode to a junction, saidconductor adapted to be parted upon removal of said electrode;

and further including two branch circuit legs; each said leg including adiode and an electrical detonator; the diodes of each leg being arrangedfor passing current of opposite polarity.

8. The apparatus of claim 7 wherein said junction and said diode, arelocated in a common chamber.

The pparatus of claim 1 wherein said electrode has a base from which anupstanding current carrying conductor depends; apertures formed in saidbase; said circuit means includes electrical conductors extendingthrough said apertures.

10. In an electrically actuated perforating gun employing a plurality ofexplosive charges therein and adapted to be placed within a well bore,the combination comprising:

a firing head for selectively firing the explosive charges;

said firing head having a plurality of electrodes contained therewithin;means electrically insulating each of said electrodes from one another;each said electrode being axially arranged relative to one another andsuperimposed one upon the other with the uppermost of said electrodeshaving a portion thereof di posed for contact with a supply of current;means by which the uppermost of said electrodes is removably supportedwithin said firing head so that when the uppermost of said electrodes isremoved the underlying electrode can be contacted by a supply ofcurrent;

circuit means electrically connecting different ones f said electrodesto different ones of the electrically actuated explosive perforatingmeans so that when a supply of current is connected to an electrode, theexplosive perforating means to which said electrode is connected will bedetonated;

and means forming a supply of current which can be brought intoelectrical contact with the uppermost of said electrodes.

11. The combination of claim and further including two diodes ofopposite polarity, said circuit means connecting one of said diodes toone said electrode and to one said explosive perforating means and asecond of said diodes to the last said electrode and to an adjacent ofsaid explosive perforating means, whereby:

a lowermost explosive perforating means may be detonated and thereafterthe polarity of the current changed so as to detonate the remainingexplosive perforating means.

12. The combination of claim 10 wherein said firing head includesaxially arranged chambers of diminishing diameters with the largestchamber being the uppermost chamber and communicating with the remainingchambers by means of shoulders,

said electrode having a base adapted to contact and be supported by ashoulder with said base being smaller in diameter than the chamberwithin which the electrode is disposed so as to enable removal thereof.

13. The combination of claim 10 wherein said electrode includes anupstanding portion which is adapted to be retrieved by an overshotapparatus.

14. The combination of claim 10 wherein said electrode includes anupstanding portion which is adapted to be retrieved by an overshotapparatus;

said electrode having a base from which an upstanding current carryingconductor depends;

apertures formed in said base; said circuit means includes electricalconductors extending through Sai apertures.

15. A perforating apparatus having separate chambers formed therein witheach chamber containing electrically actuated explosive perforatingmeans;

a firing head, a plurality of electrodes contained within said firinghead, means by which said electrodes are electrically insulated from oneanother and superimposed one upon the other and removably receivedwithin said firing head; means by which the uppermost of said electrodescan be contacted by a supply of electrical current;

means by which at least one said electrode can be removed from saidfiring head;

circuit means electrically connecting each electrode to at least one ofsaid electrically actuated explosive perforating means;

said firing head includes concentrically arranged chambers ofdiminishing diameters with the largest chamber being the uppermostchamber and communicating with the remaining chambers by means ofshoulders,

said electrode having a base adapted to contact and be supported by ashoulder with said base being smaller in diameter than the chamberwithin which the electrode is disposed so as to enable removal thereof;

whereby: a supply of current can be electrically connected to theuppermost electrode to thereby detonate one of the explosive perforatingmeans, and upon removal of an uppermost electrode, an adjacent electrodecan be contacted by a supply of current so as to detonate the explosivecharge to which it is connected.

References Cited UNITED STATES PATENTS

